1. Field
The presently disclosed subject matter relates to semiconductor light-emitting devices including LEDs, laser diodes, etc. and to a manufacturing method for the same. More particularly, the disclosed subject matter relates to semiconductor light-emitting devices as described above that emit light through an optical lens and to the manufacturing method for these devices.
2. Description of the Related Art
A conventional semiconductor light-emitting device that emits light through an optical lens, for example, is disclosed in Patent Document No. 1 (Japanese Patent No. 3,492,178). According to Patent Document No. 1, and as shown in FIG. 8, a pair of lead frames 2a, 2b is insert-formed in a casing 1 that includes a cavity 1a for reflecting the light of a LED chip 3. The pair of lead frames 2a, 2b is depicted on a bottom surface of the cavity 1a. 
The LED chip 3 is mounted on the lead frame 2a via a conductive material and has one electrode thereof that is electrically connected to the lead frame 2a. The other electrode of the LED chip 3 is electrically connected to the lead frame 2b via a bonding wire. An encapsulating resin 5 is disposed in the cavity 1a so as to encapsulate the LED chip 3. An optical lens 6 that is made from a transparent resin and is formed in a dome-shape is disposed on the cavity la that includes the encapsulating resin 5.
When the optical lens 6 is formed, the casing 1 that includes the encapsulating resin 5 in the cavity la and which includes the LED chip 3 mounted therein is placed upside down into a die 7. A liquid transparent resin is filled in the die 7 before being solidified, as shown by FIG. 9. The pair of lead frames 2a, 2b extends in both side directions from the casing 1 and operate as a stopper by contacting a top side surface of the die 7. The casing 1 is located at a predetermined position in the die 7 by the above-described operation. The optical lens 6 is formed by solidifying the liquid transparent resin in such a state. In the above process, the transparent resin becomes liquid by heating it and the liquid transparent resin is solidified by returning it to a normal or ambient temperature. Finally, the LED device is completed by removing the casing 1 from the die 7.
In the LED device such as described above, the light that is emitted from the LED chip 3 emits outside of the LED device via the encapsulating resin 5 and the optical lens 6. The light-emitting characteristic of the LED device is basically determined by the optical characteristics of the optical lens 6.
Furthermore, in the LED device as described above, phase boundaries without a chemical bond are caused between the casing 1 and the optical lens 6, and between the encapsulating resin 5 and the optical lens 6. An operating temperature of an LED device is generally in the range of −20 degrees centigrade to +80 degrees centigrade and can be a particularly wide range of −40 degrees centigrade to +100 degrees centigrade when used in vehicle applications. An LED device should be configured to operate stably within such a wide temperature range.
However, both a thermal expansion coefficient and a heat shrinkage coefficient of the casing 1, the encapsulating resin 5 and the optical lens 6 are respectively different because each uses a different material. Thus, the phase boundaries without the chemical bond are stressed by the difference of both the thermal expansion coefficients and the heat shrinkage coefficients when the boundaries are subjected to a temperature change. The phase boundaries may be peeled from each other or otherwise compromised as the case may be. For example, when the LED device is mounted on a circuit board by a reflow process, the phase boundaries are often peeled due to large temperature changes.
The peeling of the phase boundaries can result in a decrease of the light-emitting brightness because of light reflections in the phase boundaries. When materials having a high hardness are used, the peeling effect is especially prevalent. Furthermore, because the conventional LED device is located in the die 7 by the pair of lead frames 2a, 2b, the LED device can not be exactly located in a horizontal direction. Thus, an error of placement of an optical axis (O) in the LED device may result.
LED devices that are configured to prevent the peeling that can occur due to differences between the above-described thermal expansion coefficients and the heat shrinkage coefficients are disclosed in Patent Document No. 2 (Japanese Patent Application Laid Open JP2005-116817) and Patent Document No. 3 (Japanese Patent Application Laid Open JP2005-136101).
In Patent Document No. 2, an LED device is provided with a surplus storage part for holding an encapsulating resin with a high thermal expansion coefficient. The LED device may be configured to prevent peeling by providing an amount of encapsulating resin that is caused by heat shrinkage and expansion to move into and out of the surplus storage area when experiencing high and low temperatures, respectively
In Patent Document No. 3, an LED device is provided with an ease part in a part of the contact surface between a lamp house structure and an encapsulating resin in order to ease a stress that is caused in the phase boundaries between the two materials that make up these structures. In addition, cohesiveness can be increased between the encapsulating resin and the adjacent optical lens by providing a surface treatment on an inner surface of the optical lens. The above-referenced Patent Documents are listed below, and are hereby incorporated with their
English abstracts in their entireties.
    1. Patent Document No. 1: Japanese Patent No. 3,492,178    2. Patent Document No. 2: Japanese Patent Application Laid Open JP2005-116817    3. Patent Document No. 3: Japanese Patent Application Laid Open JP2005-136101
However, in the LED devices disclosed in Patent Document No. 2, providing a surplus storage part for the insufficient encapsulating resin may result in decreasing the light-emitting efficiency because the part may intercept a part of the light that is emitted from an LED chip. Moreover, because the encapsulating resin moves between the cavity and the storage part around the storage part according to a temperature change, peeling may be caused between the optical lens and locations near the storage part. In addition, because a shrinking stress is generated in the whole encapsulating resin when solidifying the liquid encapsulating resin, the peeling may be more easily caused in the above-described phase boundaries.
In the semiconductor light-emitting devices disclosed in Patent Document No. 3, the peeling in the above-described phase boundaries may be prevented due to the added cohesiveness between the optical lens and the encapsulating resin when the surface treatment on the inner surface of the optical lens is applied. The stress that is generated on the contact surface between the cavity and the encapsulating resin is partly eased by providing the expansion relief part in part of the contact surface. However, part of the expansion relief part may promote peeling in other contact surfaces outside of the expansion relief part.
The disclosed subject matter has been devised to consider the above and other problems and characteristics. Thus, embodiments of the disclosed subject matter can include semiconductor light-emitting devices and associated manufacturing methods that do not cause some of the above-described various problems and characteristics related to peeling in the phase boundaries. The disclosed subject matter can also include an LED device that is configured to decrease an optical axis positional error that is caused between the optical lens and a semiconductor light-emitting chip, and can reduce or change other associated problems and characteristics of the conventional devices and methods.